//source: http://www.movable-type.co.uk/scripts/sha1.html#code
Number.prototype.toHexStr = function()
{
    var s="", v;
    for (var i=7; i>=0; i--) { v = (this>>>(i*4)) & 0xf; s += v.toString(16); }
    return s;
}

sha1=
{
 'msg':function(msg)
 {
    var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];
    msg += String.fromCharCode(0x80);
    var l = Math.ceil(msg.length/4) + 2;
    var N = Math.ceil(l/16);
    var M = new Array(N);
    for (var i=0; i<N; i++)
    {
        M[i] = new Array(16);
        for (var j=0; j<16; j++)
        {
            M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) |
                      (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
        }
    }
    M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14])
    M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;
    var H0 = 0x67452301;
    var H1 = 0xefcdab89;
    var H2 = 0x98badcfe;
    var H3 = 0x10325476;
    var H4 = 0xc3d2e1f0;
    var W = new Array(80); var a, b, c, d, e;
    for (var i=0; i<N; i++)
    {
        for (var t=0;  t<16; t++) W[t] = M[i][t];
        for (var t=16; t<80; t++) W[t] = sha1.ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);
        a = H0; b = H1; c = H2; d = H3; e = H4;
        for (var t=0; t<80; t++)
        {
            var s = Math.floor(t/20);
            var T = (sha1.ROTL(a,5) + sha1.f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;
            e = d;
            d = c;
            c = sha1.ROTL(b, 30);
            b = a;
            a = T;
        }
        H0 = (H0+a) & 0xffffffff;
        H1 = (H1+b) & 0xffffffff;
        H2 = (H2+c) & 0xffffffff;
        H3 = (H3+d) & 0xffffffff;
        H4 = (H4+e) & 0xffffffff;
    }
    return H0.toHexStr() + H1.toHexStr() + H2.toHexStr() + H3.toHexStr() + H4.toHexStr();
 },

 'f':function(s, x, y, z)
 {
    switch (s)
    {
     case 0: return (x & y) ^ (~x & z);
     case 1: return x ^ y ^ z;
     case 2: return (x & y) ^ (x & z) ^ (y & z);
     case 3: return x ^ y ^ z;
    }
 },

 'ROTL':function (x, n)
 {
    return (x<<n) | (x>>>(32-n));
 }

}

